On Monday, the IRS revealed that a criminal syndicate's massive theft of American taxpayer data was much worse than originally thought. In May, the government agency said criminals used a tool on the IRS website to steal the tax forms of 104,000 people. It has revised that number up to 220,000.

The tax-collection agency said it realized the total number of victims was twice as high after it conducted "an extensive review covering the 2015 filing season."

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The IRS is now sending letters to those taxpayers to warn them about potential identity theft, offer free credit protection and give them an extra PIN to protect future tax filings.

The PIN program is a permanent security feature that requires taxpayers to use a six-digit passcode when filing taxes. Currently, all that is required is a Social Security number.

PINs are currently only available to tax fraud victims and residents of Florida, Georgia and Washington. The agency wants to take this pilot program nationwide.

IRS Commissioner John Koskinen said there is "no indication there is any connection" to the recent wave of fraud involving TurboTax preparation software.

But he said this is just more proof criminals are ramping up their theft of personal data for illicit gain.

"These guys are very good at data analytics. They have volumes of data available they can match up," he said. "The criminals can answer questions better than you can."